feat(interchain-token-service): calculate and save token decimals on token deployment

[fish-sammy]

Description

Todos

• [ ] Unit tests
• [ ] Manual tests
• [ ] Documentation
• [ ] Connect epics/issues

Steps to Test

Expected Behaviour

Other Notes

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 93.04348% with 8 lines in your changes missing coverage. Please review.

Project coverage is 93.50%. Comparing base (d5b5cad) to head (83e41e6).

Files with missing lines	Patch %	Lines
contracts/interchain-token-service/src/state.rs	89.79%	5 Missing :warning:
...s/interchain-token-service/src/contract/execute.rs	96.82%	2 Missing :warning:
...ntracts/interchain-token-service/src/primitives.rs	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## feat/its-balance-invariants #672 +/- ## =============================================================== - Coverage 93.51% 93.50% -0.01% =============================================================== Files 237 237 Lines 34756 34837 +81 =============================================================== + Hits 32501 32574 +73 - Misses 2255 2263 +8 ```

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